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Chemistry 1027A/B Chapter Notes -Molar Mass, Chemical Formula, Atomic Number

, Fall 2012
24 pages66 viewsFall

Department
Chemistry
Course Code
Chemistry 1027A/B
Professor
Kay Calvin

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CHEMISTRY 1100A~ NOTES A-D and
CHPT 1.
Topic A:atoms,Molecules and Moles
A.1 Atoms
-building blocks of all elements
-3 componente :proton neutron and electron
-protons-+ve
-neutrons-neutral
-electrons- -ve
proton n neutrons-found in nucleus of atom
-electrons occupy space around the nucleus
Protons n neutrons-have same mass. & make up most of the atom
-electrons small n light-1/200th of mass of a proton or neutron
Atomic Number
-all atoms of the same element have same # of protons in the nucleus ex-6 protons=C
# protons in a atom =atomic #. Atomic # of C=6 b/c 6 protons
Mass Number
mass #= total # protons +# neutrons in an atom
MASS #=NUMBER OF PROTONS+NUMBER OF NEUTRONS

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Notation azX
^mass # & atomic number of element
A-mass number
Z-atomic # , X-chemical symbol for element
-another notation chemical symbol followed by mass number ex- Na-23
ISOTOPES
-same # of protons but different # of neutrons=isotope
-same atomic #,diff mass #
ex-C-12=(6p+6n) C-14=(6p+8n)
-some elements have more then 1 isotope and there can be more then 1 isotope than
another ( 1 isotope can be more commonly found then another)
-isotopic abundance is the % by # of each of the isotopes of an element.
ISOTOPIC ABUNDANCE AND AVERAGE ATOMIC MASS
-atomic mass assigned to each element is the average value of the masses of all of the
isotopes of that element
ex- since most silicon in the world is SI-28 the average atomic mass is closer to 28u
rather than its other isotopes
AVERAGE ATOMIC MASS= PERCENT ISOTOPIC ABUNDANCE/100 X ISOTOPIC
MASS
ATOMIC MASS STANDARD
-atomic mass standard is based on the mass of C-12.
-atomic masses of all other elements in the periodic table have been measured using C-
12
-1 AMU is define as exactly 1/12 the mass of C-12
IONS
-All neutral atoms have an equal # of protons & electrons
-the atomic number Z is also # of electrons in neutral atom
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atom loses electron +ve charge = to the # of electrons lost. ex-Li 2+ ( lost 2 e- )
^ CATION (cat has paws)
atom gains electron = -ve charge ex-Li- (gained 1)
^ANION
-term ion is used for atoms that have gained or lost electrons
A.2 MOLECULES AND COMPLEX IONS
-molecules are atoms bonded together in a specific ratio-ex HNO3
-compound-molecule containing more then one element
-complex ion-are ions of molecules
diatomic-only to atoms ex-O2
polyatomic-more than 2 atoms
-# of atoms present in a molecule is determine by electronic consideration
THE MOLE AND AVOGADROS NUMBER
-impsoible to work with small # of molecules
--chemical experimentation-amount of species is expressed in moles
-one mole is the number of atoms exactly in 12 grams of C-12
Avogadros #-6.023x10^23
moles=n
-1 mole of anything is 6.02x10^23-used for atoms molecules and ions
USING AVAGADROS NUMBER
-determine # of individual atoms ,molecules or ions in a sample
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